Ok, it's no surprise. More than a few of us here are probably techno-geeks, and when you combine geekiness with a love of efficiency, you tend to wind up with a lot of overlaps. As such, I'm curious who else out there has ever done anything to improve the efficiency of their electricity usage? Probably the geekiest way would be to tune up your computer for the maximum CPU power to watts/used ratio. In case any of you are wondering how to do this, I would suggest picking up a
Kill-A-Watt, which you can buy for no more than $40 or so from a variety of retailers, some even as cheap as $30. You can see a picture of my PC plugged into the Kill-A-Watt attached at the bottom of my post in case you're curious what they look like.
Seen here in this picture, it’s basically sitting idle and only consuming 51 watts at the outlet. Anyone here have a 350 watt power supply? Maybe even a 400 or 500 watt power supply? Seeing your real power draw can be an eye-opener when it comes to just how much or how little power it takes to drive a modern computer using efficient parts. Even running my AMD Athlon at 2.07Ghz and software to fully load the CPU, the power draw is still only about 100 watts. I think this is a pretty good example of efficient computing.
For the truly geeky, I’ll include some charts and graphs too. The first one is a simple plot of what the power draw is at idle and full load (using CPUBurn) for each processor multiple. The bus speed was 166Mhz and thus the increments are 3x to 12x, plus a half step at the end for 12.5x, which is the maximum stable speed of this particular CPU. If the very last step appears flatter on the chart, it’s because it’s only a half-step speed increment rather than a full step.
It’s pretty clear to see that as you increase the clockspeed there’s a pretty linear increase in total system power draw. It would seem that the floor for this computer would probably be around 42 watts or so if the CPU was completely shut off. The power draw seems to be linear for both idle draw and maximum CPU load. The next chart was an attempt to show the total efficiency of the system as represented by the clockspeed divided by total power draw. Since at very low speeds, you don’t get much clockspeed for each watt (thanks to that 42 watts or so that is draw regardless of the CPU) what we see is sort of a power curve where the higher the clockspeed, the greater a percentage of the total power draw goes towards CPU power. If you look at the first graph again, at 500mhz and full load, it draws 57 watts. Now at 2000Mhz we have four times the clockspeed, but draw is only 68% higher at 96 watts showing that at increasing clockspeeds a greater percentage of the power drawn is converted into CPU power.
I charted both at load and at idle, but really only the loaded figures are relevant since you don’t really care about CPU cycles per watt at idle anyway. The ideal computer would be something like an Athlon64 where at idle it drops to a very low clockspeed and when loaded it increases back to a high clockspeed. Pentium4’s are also very good at doing this type of thing on their own.
So that’s all I feel like posting when it comes to computer efficiency. The other thing you can do with the Kill-A-Watt is see how much power everything else you own draws. In my livingroom for example, I have a pair of torch lamps and also an overhead ceiling fan with 4 15-watt lightbulbs. I used to use the torch lamps a lot because I thought they looked cool. Then I found out they use 160 watts on the low setting and 230 on high. That’s per lamp! Now I use the overhead light almost exclusively because even with all 4 bulbs, that’s only 60 watts of draw.
I also found it interesting that my home entertainment system draws 3 watts when in standby, about 38 watts when on but with no sound playing and only around 45 watts with music playing at a low volume. This provides additional motivation to keep the entertainment system turned off when not in use since there’s no point drawing an extra 35 watts to have it not even producing sound. My 21” monitor is actually the biggest pig of all my commonly used stuff drawing an average of 115 watts. A flat panel would certainly cut that draw, but I’m not quite prepared to run out and buy a $1200 flat panel capable of doing 1600x1200 resolution just to save $2-3 in electricity per month.
So there you have it! Have I motivated anyone to go out and find ways to meter the electricity usage of everything in their house and alter their usage patterns to the greatest benefit? Maybe? Possibly? Perhaps not at all?